Material for welding aluminum and other metals



y 4, 1963 M. F. REJDAK 3,089,798

MATERIAL FOR WELDING ALUMINUM AND OTHER METALS Original Filed April 25,1955 INVENTOR. MEL V/N/E' REJ DAK 0% fwd/db A TTO/QNEY- 3,tl39,798MATERIAL FOR WELDING ALUMHQUM AND OTHER METALS Melvin l3. Reidak,(Ileveiand, Ohio, assignor to Erico Products, Inc, (lleveland, Ohio, acorporation oft Ohio Original application Apr. 25, 1955, Ser. N 503,569,new

Patent No. 2,876,498, dated Jan. 27, 1959. Divided and this applicationApr. 14, 1958, Ser. No. 728,279

This invention relates as indicated to a novel material for weldingaluminum and other metals, and more particularly to material for use ina cast welding operation utilizing molten metal produced by anexothermic reaction.

In Patent No. 2,229,045 to Charles A. Cadwell, there is disclosed amethod of welding copper rail bonds to steel rails utilizing highlyheated molten copper produced by an exothermic reaction of the Thermittype, and such method has now been in successful commercial use for anumber of years on a large scale. Patents 2,277,014 to Noble G. Carlsonand 2,654,129 to Edward B. Nefi disclose certain preferred forms of castwelding apparatus adapted to be employed with the metal producingexothermic reaction mixture, and in application Serial No. 422,- 032 ofDonald J. Burke for Welding Apparatus, filed April 9, 1954, now PatentNo. 3,004,312, granted October 17, 1961, there is disclosed another formof apparatus particularly adapted for the joining together of twoopposed cable ends by means of a castweld connection.

For a great many years, copper wire and cable has been accepted as thestandard conductor for electric current although certain other metalssuch asaluminum and silver have been utilized in special applicationswhere their qualities are particularly desirable. In recent years,however, the use of aluminum wire and cable has. very greatly increased,and itoften becomes necessary to join aluminum cables together ortoconnect the same to copper bus bars, for example. The, molten metalproduced by the exothermic reaction mixturerdisclosed in the aforesaidCadwell Patent 2,229,045 has not proved satisfactory for the castwelding of aluminum, and prior to my present invention it has beenimpossible toobtaina connection which isrboth physically strong and ofsubstantially unimpaired electrical conductivity.

it is accordingly a principalobject of this invention to provide amaterial for cast welding aluminum articles, and more especially forcast welding aluminum conductors such as cable to other cable, bus bars,grounds, etc.

Another object is to provide such method of welding which is nothindered by the usual oxide film found on articles of aluminum.

A further object is to provide such material and method of weldingutilizing an exothermic reaction mixture to produce the molten weldmetal in situ at the proper temperature and under properly controlledconditions.

Still another object is to provide a cast welded connection wherein theweld metal is interfused with the aluminum article or articles.

Other objects of the invention will appear as the description proceeds.

To the accomplishment of the foregoing and related ends, said inventionthen comprises the features hereinafter fully described and particularlypointed out in the claims, the following description and the annexeddrawing settingforth in detail certain illustrative embodiments of theinvention, these being indicative, however, of but afew of the variousways in which the principle of the invention may be employed.

Said annexed drawing is a semi-diagrammatic crosssection through agraphite crucible and associated mold cavity adapted to receive twoopposed cable ends to be cast welded together.

hired Fascias @E ee 3fid9fi98 Patented May 14, 1963 Referring now moreparticularly to such drawing, the welding apparatus may comprise twographite blocks such as l hollowed out to provide an upper crucibleportion 2 and mold cavity portion 3, the two halves being temporarilyclamped together as shown and described in Burke application Serial No.422,032, for example. Two dry and clean cable end portions 4 and 5 areclamped in the mold cavity with their opposed ends located substantiallyvertically below sprue 6 which is closed by means of a small metal disc7, ordinarily steel. The exothermic reaction mixture which may besupplied in the form of a cartridge is emptied into the crucible so thatthe principal metal forming materials 8 fill the lower portion of thecrucible and the starting powder 9 forms a layer on top. Such startingpower may then be ignited with a flint gun, and it in turn ignites theexothermic reaction mixture to produce the molten metal charge whichmelts through disc 7 and drops into mold cavity 3, surrounding the cableend portions and bonding thereto. The mold may then be opened and thewelded connection removed.

As previously indicated, it has proven extremely dithcult to obtain asatisfactory weld where aluminum articles are concer ed, as for examplewhen attempting to weld aluminum cable to a copper bus bar. Not onlydoes the aluminum conduct away heat with great rapidity, but also thethin film of aluminum oxide normally covering its surface is highlyrefractory in character and militates against the obtaining of a trueweld in which the metal of the aluminum article is intimately interfusedwith the weld metal. I have found that a satisfactory weld, and moreparticularly a weld of good physical strength and electricalconductivity, may be obtained by the employment of molten tin or tinalloy as the weld metal which is so highly heated that it is eiiectiveto melt a portion of the aluminum (including aluminum alloy) articlewhile covering such melted portion and preventing contact with theatmosphere. The thin refractory aluminum oxide film is thus locallyflushed away and true inter-fusion of the underlying aluminum with theweld metal is obtained.

1 have further discovered that such weld metal may desirably be producedby an exothermic reaction between stannic or stanuous oxide andsufficient aluminum to reduce such oxide, sufiicient additional metalbeing present in the reaction mixture to control the violence of thereaction and to form an alloy with the tinmetal produced thereby ofproper strength, ma-lleability and electrical conductivity.

I have also discovered that certain selected fluxing agents whenincorporated in the exothermic reaction mixture greatly facilitateproper carrying out of the operation.

Ordinarily, not only is aluminum the preferred reducing agent for thetin oxide, but it is also the preferred metal for inclusion in thereaction mixture to regulate the reaction and alloy with the molten tinproduced thereby.

The basic reaction using stannic oxide may be written as follows:

3SnO +4A1 2Al O +3Sn or stated by parts by weight:

37 parts SnO +9 parts Ale 26+ parts Sn Using stannous oxide, the,reaction may be Written:

3Sn0+2Al- 1Al O +3Sn, or 32 parts SnO+4 parts Al 28 parts Sn An excessof 17 parts aluminum powder ordinarily yields the best results. Thisexcess aluminum not only serves to moderate, regulate and control theotherwise too violent exothermic reaction, but also alloys with themolten metallic tin produced to form a highly heated molten alloycapable when dropped into the mold cavity of interfusing with thealuminum cable end portions to form a strong malleable cast weld. Thetemperature of such molten charge will preferably be in excess of 2,000F. and the cast weld metal is accordingly enabled actually to meltportions of the cable and wash away the refractory oxide film thereon toform an integral weld. The aluminum cable or other aluminum article mayalso be cast welded by my new process to articles of brass, bronze, andNichrome. In these cases, both the aluminum article and the otherarticle are interfused with the cast weld metal. Copper, steel,stainless steel and cast iron articles may also be bonded to aluminumarticles in accordance with my invention if properly prepared, as bydipping in molten tin, so that the cast weld metal will braze thereto.

By far the preferred fluxing agent which may be included in theexothermic reaction powder mixture is calcium fluoride. A proportion ofcryolite or sodium chloride may be included therewith.

The following examples of suitable exothermic reaction powderformulations for welding aluminum in accordance with my invention aregiven by way of illustration only and are not to be considered aslimiting the invention. They are arranged in order of preference and thepercentages given are by weight. In each case aluminum powder isemployed as the oxide reducing agent and also as the excess metalincluded for the purpose of regulating the reaction:

Example 1 Percent Tin oxide 56.0 Aluminum powder 39.4 Calcium fluoride3.0 Cryolite 1.6

Example 2 Tin oxide 65.0 Aluminum powder 24.5 Calcium fluoride 10.5

Example 3 Tin oxide r 61.8 Aluminum powder 28.4 Calcium fluoride 6.6Cryolite 3.2

Example 4 Tin oxide 58.8 Aluminum powder 36.5 Calcium fluoride 3.6Cryolite 1.1

Example 5 Tin oxide 57.8 Aluminum powder 39.0 Calcium fluoride 1.6Sodium chloride 1.6

Example 6 Tin oxide 54.4 Aluminum powder 42.6 Calcium fluoride 1.4Cryolite 1.6

Example 7 Tin oxide 47.4 Aluminum powder 50.0 Calcium fluoride 1.3Sodium chloride 1.3

As previously indicated, certain other metals may be included in theexothermic reaction mixture for the purpose of regulating the sameinstead of the excess aluminum provided in the examples given above. Ingeneral, an amount of aluminum powder will be included slightly morethan the theoretical amount required to reduce the tin oxide present andthen approximately 20% by weight of nickel, tin, silver, iron, orchromium may be included instead of the excess aluminum. Of course, whentin metal constitutes such excess, the resultant molten charge will besubstantially entirely tin with only quite small amounts of aluminum,iron, etc. Illustrative examples of exothermic reaction mixtureformulations in accordance with my invention in which a metal other thanaluminum is utilized to control the reaction and to alloy with themolten tin produced are given below:

Example 8 Percent Tin oxide a 59.5 Aluminum powder 14.7 Silver 21.0Calcium fluoride 3.2 Cryolite 1.6 Example 9 Tin oxide 60.5 Aluminumpowder 14.5 Nickel 19.7 Calcium fluoride 3.3 Cryolite 2.0 Example 10 Tinoxide 60.5 Aluminum powder 14.8 Iron 18.0 Calcium fluoride 6.7 Example11 Tin oxide 58.5 Aluminum powder 14.3 Tin 22.2 Calcium fluoride 3.2Cryolite 1.8 Example 12 Tin oxide 61.8 Aluminum powder 14.7 Chromium13.6 Calcium fluoride 9.9

Stannic oxide is commercially available in particle sizes of from about0.5 to about 1.5 microns, and such material has proven very satisfactoryfor my purpose although somewhat larger size particles are alsosuitable. A suitable particle size for the aluminum powder and othermetals present in the reaction mixture is approximately 325 mesh. Itwill be appreciated that the excess metals employed for the purpose ofregulating the reaction may include one or more of the several metalsindicated above as suitable for this purpose. is that they shall not bevolatilized by the heat of the reaction and will alloy with the moltentin to form a. strong malleable cast weld of good electricalconductivity.

A suitable ignition powder formulation is as follows:

Various other suitable ignition mixtures are well known in the art. Theymay themselves be ignited in most satisfactory being various ways, thesafest and through use of a flint gun.

In general, other reducing agents known and employed The principalrequirement in various prior art Thermit reactions are not nearly assatisfactory as aluminum, some of them producing reactions even moreditlicult to control and forming less satisfactory alloys with the metaltin. Consequently, aluminum is by far the preferred reducing agent.

The preferred alloying metals indicated above have relatively highboiling points, high latent heats of fusion and are capable of alloyingwith the tin to form malleable cast welds with good electricalconductivity. The alloying metals should have boiling points not lowerthan 3500 F. The most suitable alloying metals listed above have boilingpoints as follows:

Silver 4010 Nickel 4950 Iron 4960 Tin 4120 Chromium 4500 Aluminum 3740Aluminum has a melting point of 1220 F. and tin has a melting point of449 F. The alloys produced by reaction of the exothermic reactionmixtures listed above all have melting points below 2000 F.

It will be seen from the foregoing that l have provided a novelexothermic reaction mixture which permits me to Weld an aluminum articleto another metal article by igniting such exothermic reaction mixture toproduce highly heated molten tin or an alloy thereof having atemperature in excess of 2000 R, such molten metal immediately beingdelivered to a mold cavity defined in part by such articles to bejoined, the heat content of such molten charge causing a portion of thealuminum article to interfuse therewith to form a strong malleableconnection. lin certain cases, the heat of such molten charge may be ashigh as 3000 F.

Stannous oxide, while also suitable for use in the reaction, is tooexpensive for ordinary commercial use. The specific examples given aboveaccordingly employ the stannic oxide. The molten metal produced by myexothermic reaction will ordinarily and preferably comprise a majorproportion of tin by weight.

This application is a division of my co-pending application Serial No.503,569, filed April 25, 1955, now Patent No. 2,870,498.

Other modes of applying the principle of the invention may be employed,change being made as regards the details described, provided thefeatures stated in any of the following claims or the equivalent of suchbe employed.

I therefore particularly point out and distinctly claim as my invention:

1. An exothermic reaction mixture for the production of highly heatedmolten weld metal consisting essentially of 37 parts by weight ofstannic oxide and from 17 to 40 parts of metallic aluminum powder.

2. An exothermic reaction mixture for the production of highly heatedmolten weld metal consisting essentially of 37 parts by weight ofstannic oxide having a particle size of from about 0.5 to about 1.5microns and approximately 26 parts of metallic aluminum powder havaparticle size on the order of 325 mesh.

3. An exothermic reaction mixture for the production of highly heatedmolten weld metal consisting essentially of Percent by Weight Stannicoxide 56.0 Aluminum powder 39.4 Calcium fluoride 3.0 Cryolite 1.6

4. An exothermic reaction mixture for the production of highly heatedmolten weld metal consisting essentially of stannic oxide, sufficientaluminum powder to reduce said oxide, and approximately 20% by weight ofthe entire mixture of an alloying metal selected from the classconsisting of nickel, tin, silver, iron and chromium.

5. The reaction mixture of claim 4, including a small amount of calciumfluoride as a fiuxing agent.

6. An exothermic reaction mixture for the production of highly heatedmolten weld metal consisting essentially of 37 arts by weight of stannicoxide, from 17 to 40 parts of metallic aluminum powder, and a smallamount of calcium fluoride as a fluxing agent.

7. An exothermic reaction mixture for the production of highly heatedmolten weld metal consisting essentially of tin oxide, a reducing agenteffective to reduce said oxide to produce molten tin, and sufiicientmetal powder selected from the class consisting of tin, aluminum,nickel, silver, iron and chromium to regulate the reaction to reventviolent spattering and substantial loss of such molten tin and to reducethe temperature of the resultant molten alloy to a figure not less than2,000" F.

8. The reaction mixture of claim 7, including a small amount of calciumfluoride as a fiuxing agent.

References @ited in the file of this patent UNITED STATES PATENTS440,952 Land Nov. 18, 1890 1,430,667 Merrefield Oct. 3, 1922 1,750,162Deppler Mar. ll, 1930 2,106,259 Stockmar Jan. 25, 1938 2,831,760 RejdakApr. 22, 1958

1. AN EXOTHERMIC REACTION MIXTURE FOR THE PRODUCTION OF HIGHLY HEATEDMOLTEN WELD METAL CONSISTING ESSENTIALLY OF 37 PARTS BY WEIGHT OFSTANNIC OXIDE AND FROM 17 TO